Q. A nichrome wire $50\ cm$ long and one square $millimetre$ cross-section carries a current of $4A$ when connected to a $2V$ battery. The resistivity of nichrome wire in $ohm\ metre$ is
A) $1 \times 10^{- 6}$
B) $4 \times 10^{- 7}$
C) $3 \times 10^{- 7}$
D) $2 \times 10^{- 7}$
Explanation
(a) $R = \frac{V}{i} = \rho\frac{l}{A} \Rightarrow \frac{2}{4} = \rho\frac{50 \times 10^{- 2}}{\left( 1 \times 10^{- 3} \right)^{2}} \Rightarrow \rho = 1 \times 10^{- 6}\Omega m$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.